Specific function of B-Raf in mediating survival of embryonic motoneurons and sensory neurons

Embryonic sensory and motoneurons depend on neurotrophic factors for surviv al. Here we show that their survival requires B-Raf, which, in this functio n, cannot be substituted by C-Raf. Sensory and motoneurons from b-raf-defic ient mice do not respond to neurotrophic factors for their survival. Howeve r, these primary neurons can be rescued by transfection of a b-raf expressi on plasmid. In contrast, c-raf-deficient neurons survive in response to neu rotrophic factors, similarly to neurons from wild-type mice. This points to an essential and specific function of B-Raf in mediating survival of senso ry and motoneurons during development.